Why do people get so exercised about what other people do with their boats? Why do you care?
Also, everyone's circumstances are different. Not everyone who owns a boat but doesn't use it much is a bad person. For sure, there are people who neglect their boats because they generally are careless people, but I suspect they are in the very small minority in most places.
Finding time to use a boat for the average person is not so easy. Most people have to work, they have families, they have other commitments/interests. Take the guy who loves boating but has kids. The guy works during the week, so that time is out. His kids play baseball or whatever, so just about every weekend he's at the baseball diamond, soccar field, etc. That guy might love sailing, but his all-too-common circumstances conspire to prevent him from using his boat that much. Don't be so hard on him. He's suffering plenty all on his own. And this example doesn't even contemplate the reluctant spouse or any of the other myriad of factors that plague the average recreational sailor, not to mention that someone might have the gall to want to do something else on a weekend during the summer every now and again.
Even for devoted and avid sailors, it's hard to find time to get on the water, unless you're independently wealthy. If you figure that the sailing season, at least in the mid-Atlantic/northeast area, is about 5 months on average, that's about 20 weekends. That means for the most avid sailor, you are looking at the boat moving 40 days out of 150 in season, if it's used every day of every weekend, which is just not realistic (think about bad weather, sickness, boat breakdowns, cousin's wedding, etc.).
I consider us devoted and avid sailors as a family, but my situation illustrates the point. My wife and I love being on the water, and we have two young boys that hopefully will feel the same way as they get older (for now they come with us because they have no choice). We get the boat in the water as early as possible every Spring, and stay in late into the Fall, which means we go in early April and come out October/November (one of the reasons we have that enclosure is to stretch the sailing season). We take several weeks each summer to cruise (no less than two weeks, usually in the neighborhood of three, sometimes more if we're lucky). We also use the boat every weekend we can, most of them involving an overnight in a local harbor. I think we use our boat more than most people do. Still, our boat sits on her mooring far more than she doesn't. Think about it, if we want to take our boys to a Yankee game on a Saturday afternoon, that knocks out going away for that weekend, or even using the boat that Saturday, and there you have it, one of those precious weekends gone. That would mean our boat would sit for 12 straight days without being used in the middle of July (for example), and an onlooker hanging around the harbor could see our boat on the mooring and say, "what a shame for that boat to be just sitting there so much." That's just life for us, and it is for many others as well. And for us I suspect it will get worse before it gets better. When our boys start to have their own activities, it will be harder to get on the boat early Saturday morning and stay on until Sunday evening. We're starting to experience that already with birthday parties and the like.
And here's another thought. If the "rule" were that you shouldn't be allowed to have a boat unless you use it all the time (however defined), very few people would have boats. And that means there would be no sailing community or industry because there would not be enough customers to sustain the industry from an economic perspective. So, be thankful for all those people who have boats and pay people to store and maintain them, even if they don't use the boats that often. In fact, those people should be your best friends. They help sustain the industry that provides the goods and services you want to use, yet they do not clog up the harbors. I bet the people who complain loudest about people not using their boats also complain about how the best anchorages are too crowded.
So, the point is that you shouldn't be too judgmental of people who use their boats less than you think they should. Everyone's circumstances, desires and interests are different.
I'd quote Dennis Miller and say I don't want to get on a rant here, but it's too late at this point.